Drugs in extensive clinical use and beset with frequent adverse reactions provide opportunities for eulucidating the effects of age and disease on drug disposition and pharmacologic effects during therapy. Studies of prednisolone and prednisone pharmacokinetics in pediatric and adult patients with asthma, with nephrotic syndrome, in nursing women, and in patients who are overly sensitive or resistant to therapy will characterize the effects of age, alteration of protein binding, and renal disease on drug disposition in relatively normal and in severely altered pathophysiologic states. The utility of saliva concentrationa as a noninvasive method for measuring non-protein bound drug will be examined. Improved high performance liquid chromatographic assay methods will be sought for pediatric applications. Pharmacokinetic and statistical methodology will be developed to optimize data collection in children, account for nonlinear protein binding and tissue distribution, characterize biological rhythms in pharmacokinetics, and assist in prediction of drug disposition in individuals from a population.